The present invention relates to lithographic printing plate supports obtainable using an aluminum alloy plate, and to presensitized plates for lithographic printing obtainable from such supports. The invention also relates to methods of manufacturing such lithographic printing plate supports and presensitized plates.
Aluminum alloy plates are generally produced by using a semi-continuous casting process (direct chill casting) to cast a slab from an aluminum alloy melt, then subjecting the slab to homogenizing heat treatment, followed by hot rolling, cold rolling and, if necessary, annealing.
To produce aluminum alloy plates continuously by a simpler process than semi-continuous casting, various continuous casting processes have been proposed which use a driven, or moving, mold that casts the plates directly from the aluminum alloy melt.
Continuous casting processes which use such a moving mold include processes that employ a moving mold in the form of a pair of belts, such as the Hazelett process, and processes which employ a moving mold in the form of a pair of rolls, such as the Hunter process and the 3C process. In the Hunter process, a pair of cooling rollers are tilted about 15° from the vertical and the aluminum alloy plate is cast in an upwardly angled direction. In the 3C process, a pair of cooling rollers are arranged vertically and the aluminum alloy plate is cast in the horizontal direction.
An advantage with such processes which use a moving mold is that the equipment can be compact. Processes which use a moving mold in the form of rolls are especially outstanding in this respect.
In a process that uses a roll-type moving mold, the aluminum alloy melt (also referred to below as an “aluminum melt”) is fed between a pair of cooling rollers by a melt feed nozzle, and solidification and rolling of the aluminum melt are carried out by the cooling rollers as a single operation. Processes which use roll-type moving molds are described in detail in U.S. Pat. No. 2,790,216, CA 619,491, JP 51-15968 B, JP 51-89827 A, JP 58-209449 A and JP 1-215441 A.